ABC News(LOS ANGELES) — Southern California is bracing for torrential rain and powerful winds Friday in what could be the strongest storm to hit the region in years, if not decades.

The massive storm took aim at the West Coast Friday morning and will dump heavy rain across southwest California Friday, with numerous rain showers lingering into Saturday, according to forecasts. Flash flood watches are in effect for Los Angeles, Ventura and Santa Barbara counties from Friday morning through Saturday morning.

“The storm looks to be the strongest storm to hit southwest California this season,” the National Weather Service office for the Los Angeles region wrote. “It is likely the strongest within the last six years and possibly even as far back as December 2004 or January 1995.”

The storm is expected to generate a total of 3 to 6 inches of rain in Los Angeles County beaches and valleys and 5 to 10 inches of rain in south-facing foothills and coastal mountain slopes, according to the National Weather Service.

Heavy rainfall and gusting wind moved into Southern California Friday around 7 a.m. local time. Los Angeles will start to see the heaviest downpour Friday afternoon. By 6 p.m. local time, heavy rainfall will move further south into San Diego, according to ABC News meteorologists tracking the storm.

With soil already soaked from significant rainfall this winter, forecasters warned of the potential for flash floods and debris flows, especially near areas stripped bare by wildfires.

“A combination of the Pacific jet stream and a storm system will bring copious amounts of rain to Santa Barbara, Los Angeles and San Diego today into tonight,” said ABC News senior meteorologist Max Golembo. “This will lead to major flash flooding in urban areas. Mudslides and rockslides are possible in the recent burn areas.”